Getter for electron discharge device



Aug. 11, 1959 E. A. LEDERER 2,899,257

GETTER FOR ELECTRON DISCHARGE DEVICE Filed Sept. 26. 1955 /IAW Fig.3.

Ernest A .'Lederer ATTORNEY States Patent 7 2,899,257 GErrER FOR ELECTRON DISCHARGE DEVICE Ernest A. 'Lederer, Essex Fells, NJ., assignor to West- -t..inghou'se. Electric Corporation, East Pittsburgh, Pa., :1 corpora tion; of Pennsylvania ,w A p afi j S ptember 26, 1955, Serial No. 536,377

' 12 Claims. (Cl. 316-25) .This invention relates to electron discharge devices and" more particularly to the use in such devices of chemically active gas clean-up materials known as getters.

I A getter is a material used to reduce the pressure of the residual gases in an evacuated electron discharge deyice either during or after the mechanical exhaust process.

Afgetter should be inertunder ordinary conditions but 2 'shouldb'e of such: a character that it can be made highly moves theresidual gasby'either chemical or physical tubes. and image intensifiers, and may cause other defects in'fthes'e and other types of electron discharge devices.

"In generah jaccording to my invention, I propose that suitableporous, inert andrefractory bodies, which have been impregnated with an appropriate material such as bariumazi-de (BaN be used as getter devices.

iffTherefore', it is an object of this invention to provide animp'roved getter device for electron discharge devices. It isfafurtherobjectvof this invention to provide an improvedgetter' device for electron discharge .devices whichmin' es the number of loose particles in an elect'r'bn discharge'device.

These and other objects of the invention will be apparentirom the following description, taken in accordance with the accompanying .drawing' which forms a 'part of'this application, and in which: I

'j l Figure 1 is a perspective view of an electron discharge device embodying my'invention, the glass envelope and the'anode being broken away to show the interior struc- ;:Fig.- '2 is a perspective View of one embodiment of 'a W 4 'getterdevice'constructed according to my invention;

@lFig-(B is'a view, partly in section, of another embodiment of the getter device constructed according to my i v o L Fig. 4 is a top view of a getter device and getter 7 support member-similar to that shown in Fig. 1;

z Fig.6 is a schematic drawing of a method for con- 'structin'g'getter devices according to my invention; and Fig. 6 is a view of getter devices constructed by th method shown in Fig. 5. a

In Fig.- 1, there is shown an electron discharge device embodying my invention including a cathode electrode 11 isurrbundediby. a .grid electrode 13 which, in turn, is surrounded by an, anode electrode 15. A glass envelope 23.,encloses the electrode structure. Mica spacers 17 and 19- and lead-in. wires 21 are also shown. The getter device ZSis supported by the getter support member 27 which is attachedrtov the micaspacer 17. If desired, to 'minimizespurious electrical charges, the getter support member; Z'Lmay be electrically connected to the cathode uudathereforetothegrouud.

2,899,257, Patented Aug. 11, 1959 'ice 2 In Fig. 2, there is shown a, getter device constructed according to my invention, including a wire heater member 29 upon which a ceramic body or getter carrier mem ber 31 has been placed. The ceramic getter carrier member 31 should be constructed of a material which isinert with respect to the getter material used. I In one embodiment of my invention, the material should be inert with respect to barium azide and metallic barium. Suitable ceramic mate'rials'are aluminum oxide, magnesium oxide, beryllium oxide, thorium oxide and zirconium oxide. Suitable materials from which the wire heater members may be made include nichrome, tungsten, molybdenum and similar refractory metals or alloys.

In Fig. 3, there is shown a getter device constructed according to another embodiment of my invention in which a wire heater member 35 is enclosed by a ceramic tube member 33.- The wire heater member 35 may be any of the known types of heaters, such as coil, straight or folded heaters.

In Fig. 4, there'is shown a top view of a'getter device similar to that shown in Fig. 1, in which a wire heater member 39 has been enclosed in a ceramic getter carrier member 37 and is supported by a getter support member 41. The getter support member 41 may be constructed of iron wire and the getter device may be heated by induction heating. j If desired, the getter device may be connected across lead-in wires and heated by the current from the lead-in wires. I V

In'Fig'. 5, there is shown a schematic drawing of a method for constructing a getter device'according to my invention, in which wire heater menibers'45 are drag co'atedwith a' suitable ceramic material such as aluminum oxide by pulling them through rollers 43'. The coated heater members 45 are then fired in accordance with wellknown ceramic practice and may be oVeIcoated with additional ceramic material forming a structure 'such as that shown Fig. 6, including the w ire'heater members 45' and the ceramic coating 49. The coated heater wires are then immersed in a saturated solution of barium aizide water and after a suitable soaking period, the getter device'is' dried at roo m temperature. If anaccelerate'd dryingprocess'is"desired, the temperature should not'ex} ceed C. "After drying, the ceramic material is stilt porous but barium azide hasbeefl distributed'throughout the ceramic getter carrier member. The getterdevice is mounted 'in'an electron discharge device which is then evacuated. If the getter device is heated for a short time to a temperature of appr-bximately;400 C.',' the bariuma'zide" will 'be' decomposed into its constituents, barium-and nitrogen, and the nitrogen gas formed may be removed by vacuum pumping. At; the temperature of approximately 400 C., the vapor pressure of the free barium metal is so low that substantially no evaporation takes place. Upon raising the temperature of the getter to approximately 700-800 C., barium metal will evaporate therefrom; It may be desirable'for 'a part of the barium metal to remain within the ceramic getter carrier member especially if it is impractical to evaporate tall the barium because of lack of space for deposition of the metal. Because of the porosity of the ceramic getter carrier member, the barium metal. distributed therein provides a very large surfaceto the residual gas and thus aids in its removal. I w v Instead of using an inert, porous and refractory body as the getter carrier member, it may be. advantageous incertain cases tosubstitute a porous metal forjthe ceramic material. This porous metal should be inert with respect tobarium metal, i.'e. ,-no alloying should take place. ;The porous. metal gettercarrier member-should alsobe refractoryv and itshould be easily prepared in a emus p t-s qn yz isms-a. Sui abl .ma sr l P F ma n colurnbium. These metals are particularly desirable besa olcam per ies. .lfmetalis'u ied1ast s tter lcarrier member, the heater wires must beinsul ated Utilizing the dess b e hniq e 'omb nc w th and ceramic or powder-metallurgical'practice getter devices m e. Pr p d whic d not xp o n ,o or o "small particles; Because of its surface tension, molten b mm will a e ts c o sly o t e-tpo ushody t t i is r m l ik y thatsolid barium Pa icles would fall off the carrier, While barium azide may give sh-a m m t P es hen hcste t o apidly.

the disclosed technique which embodies close mechanical 2'.

land thermal contact between an inertand n a ti ematerial precludehotspots and localexothcrmio rcacr tions. t

If desired, the getter device may be flashed in specified directions by using suitable shields andsupport .constructions. Also, in electron discharge devices where, a getter deposit on the envelope is detrimental, the getter device may befheated onlyfor suchperiods andsuchtempera' tures that it is made highlyabsorptive,

- Another advantage of; a getter device such as tha-tdiscloscdinmy invention is thatit is easily adaptable to special requirements such as the requirementof low current but a relatively high fiashingvoltagc, For example, if high-frequencyinduction heating is used, such as with ea Shou b low. o heating withounomsupplied through lead-in wires, itmay be advantageous to use a long, fine heater wire of high specific resistancemade in .a coil.

While the assertiveness" been Show at. its a io msflonly, il a ill be obvious to those skilled in theiart rhatit is notgso limited but is susceptible .of various chang n modifications .withoutdeparting. from the spirit and scope thereof. f a

,For example, the present invention is not limi ed. to the use oflb um azidelas a sourceofactive material, as active barium may be. obtained, in yarioushways as is known iutheart. Of course, other active materials than bariummaybe used, such as otheralkaline earth metals. Also, if desired, thesource of active material may-be separatedfromthe porous body which is utilized because of its large surface. I claim asmy invention: v 1. A gas. cleanup de' ice. comprising a porous refractory body, said body being impregnated with amaterial which liberates a, chemically active substance upon heating. said body being inert. with respect to said chemically active substance, v a a 2. Asource of barium comprising a porous refractory body, said body being impregnated with a barium containing material which liberates barium upon heating said body being inert with respect to barium. 3. A getter device for an electron discharge device comprising a porous refractory body, said body being impregnated with barium azide, said body being inert with'respecbto barium.

4. A getter device for an electron discharge device comprising a porous refractory ceramic body, said body being impregnated with a salt of hydrazoic acid and a metal selected from the group consisting of the alkali i comprising a porous refractory body of ceramiccomposition, said ceramic composition being selected from the group consisting of'oxides of aluminum'magnesium,

beryllium, thorium and zirconium, said body being impregnated with barium azide. 6. A getter device for an electron discharge device comprising a porous body of refractory metal, said body being impregnated with a material which liberates a chemically active substance upon heating said body being inert with respect to said chemically active substance.

7. A getter device for an electron discharge device comprising a porousbody of refractory material, said refractory material being selected from the group com sisting of zirconium, titanium, hafnium, thorium, tantalum, columbium, tungsten, molybdenum, cobalt, iron, nickel and the eutectic alloyof aluminum andpccl'il nr, said body being impregnated with barium azide.

8. A method of introducing active metal into an electron discharge device, said method including the steps of impregnating a porous refractory body which is inert with respect to said active metal with a materialwhi h liberates s id a tive nenllu on heati g; nd h iiqs aid impi s t P ro refractory b t to l be ate said active metal. V 9. A method of. introducing an active'metal ntoen electron disch rgodevice'havingan envelope s id method including the steps of impregnating a porous refractory ody. hi h is iniat a r s as dI s i a we; with amaterialwliich liberates said a ave matcrielupon heating, mounting said impregnated porous refractory. bQClY within said envelope of said electron discharge device, heating said body to decompose said matcrial' nd liberate said active metal and evaporating at least para e metalfrom said body.

10. A method. of introducing barium into el ctron the device shown in Big. 4, the resistance of the getter 5 discharge devicfi having an finvel'gplisaidfmethod'mf cluding the steps of impregnating with barium azide' a porous refractory body of. ceramic compositor, selec ed from the group consisting of oridesiof al miuum, Inasnesium,- beryllium, thorium 1 and lil'Po iiqngy, mounting said impregnated body within said envelopes)? Said 91cc tron discharge device, ea in said body we temp; to ofapproximately 400 to dccolnppse barium 5 into barium and n trog n, removing the nitrogeudroni said envelope and heating. said body to atcmpr il o appr xi a ly 0 Q W 12 'at 19%. .Bi 'i of the barium from said body '11. A method of introducing bar'iunrjnto electron discharge devicehaving an envelo e, l said-imethodincluding the teps of i pregn n wit a ium aside a porous body of refractory metal selected from the'group consisting of zirconium, titanium, hafnium, thonunr, tantalum. col mbium; t ngsten, molybdenum, cobalt, iron, nickel, and the eutectic alloy aluminum mounting said m r ate eauti Said enclos o said electron discharge device, heating said body to a temperature of approximately 400? coo decompose t barium azide intobarium and nitrogem' removing the n trogen from said envelope and heatiugs id o ytto a temperature of approximately 7Q0f -800" C. to evaporate at least part of the barium from said body.

12. A source of an alkaline earth metal. comprising a porous refractory body, said bodybeing impregnated .With a material containing an alkaline earth metahsaid body being inert with respect to. said alkaline earth metal, said material liberating said alkaline earth metal upon heating. @w ,z

References Cited in the file of this patent? UNITED STATES PATENTS 1' Weller .Nov. '2; 1926 Lederer Notice of Adverse Decision in Interference In Interference No. 90,977 involving Patent No. 2,899,257, E. A. Lederer, Getter for electron discharge device, final judgment adverse to the patentee was rendered Aug. 23, 1962, as to c1aims'2, 8, 9 and 12.

[Oflicial Gazette December 4, 1.962.]

Notice of Adverse Decision in Interference In Interference No. 90,977 involving Patent No. 2,899,257, E. A. Lederer, Getter for electron discharge device, final judgment adverse to the patentee was rendered Aug. '23, 1962, as to claims *2, 8, 9 and 12.

[Ofiieial Gazette December 4, 1962.] 

1. A GAS CLEANUP DEVICE COMPRISING A POROUS REFRACTORY BODY, SAID BODY BEING IMPREGNATED WITH A MATERIAL WHICH LIBERATES A CHEMICALLY ACTIVE SUBSTANCE UPON HEATING SAID BODY BEING INERT WITH RESPECT TO SAID CHEMICALLY ACTIVE SUBSTANCE. 